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Please post the output of your ssh command, with "-vvv" added, ie "ssh -vvv myname@myhost", so we can see where in the connection your issue is occurring. Without any error message or debug output, any suggestions will be just guessing. It could be a firewall issue, it could be a DNS issue....
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Don SimonOct 30 '12 at 20:05

if no try to nslookup (win/ubuntu) or dig (ubuntu) this maschine and look how it resolves the IP you're trying to reach.

It could be possible that you're using the false port, normally it's 22, but if it there is a possibility to connect over the internet it should be changed to an different one.
Otherwise a dump crawler, trying to connect to whatever he founds has chances to get into this system.